Reference Standard. The reference standard used for calibration has one half of its working surface cad-
mium plated. This provides the user an opportunity to identify conductivity changes related to cadmium plating varia-
tions. The reference standard has been covered with a layer of teflon tape to (1) protect the cadmium plating and (2)
provide a facsimile of the lift off encountered from the main rotor hubs painted surface.
NDI Equipment Settings.
a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19eII.
Refer to Eddy Current Method, paragraph 1.4.11, TM 1-1520-253-23
b. Set up on the reference standard as follows:
Place a piece of teflon tape across the probe tip. Replace as necessary.
Null the probe on the test block.
Adjust phase as required to obtain horizontal lift-off.
(4) Slide the probe over all three notches in test block. Adjust gain to obtain a three block vertical sig-
nal when probe is passed over the 0.040 inch notch. Refer to the standard instrument display shown in Figure 1-7,
(5) Note the differing conductivity locations of the flying dot with the probe placed on the non-cadmium
plated portion of the reference standard versus the probe located on the cadmium plated portion. Reference Figure
Figure 2.15B displays the conductivity variation between
Cadmium variations will raise or lower the flying dot along
the dotted line representing the conductivity curve as
conductivity values change.